Block House Explained

Block House Explained

3 Min.

A block house is a brokerage firm that arranges large trades between institutional buyers and sellers, called block trades. These trades involve substantial assets, often exceeding $200,000 in bonds or 10,000 shares of stock. Block houses act as intermediaries, breaking down large trades to minimize market disruption. The fourth market allows direct block trading without brokerage involvement, reducing risks like market manipulation and insider trading.


A block house is a brokerage firm with a unique focus on connecting institutional buyers and sellers involved in substantial trades. These transactions, termed block trades, typically involve large sums, often surpassing $200,000 in bonds or 10,000 shares of stock, excluding penny stocks. These trades occur off-exchange to prevent adverse impacts on market prices.

Unlike standard brokerage firms, which deal with various trade sizes, block houses primarily handle block trades. The role of a block house is to facilitate these trades between parties while serving as an intermediary. They earn revenue through commissions and transaction fees.

Block House Trading Process

  1. Trade Definition: Block trades are defined as transactions exceeding $200,000 in bonds or 10,000 shares of stock.
  2. Intermediary Role: The block house acts as a middleman, enabling trades between buyers and sellers without using a public exchange.
  3. Reducing Market Disruption: To prevent excessive market volatility caused by large trades, block houses divide block trades into smaller segments, minimizing disruptions.
  4. Market Impact: Even well-executed block trades can influence the market. Analysts monitor block trade activity to predict market trends. For instance, if a mutual fund manager acquires a significant amount of stock in a particular industry, it might indicate a future upward trend.

Institutional Clients

Block houses serve institutional clients, including corporations, banks, insurance firms, mutual funds, and pension funds. These entities engage in block trades due to the potential impact on market prices caused by large transactions.

The Fourth Market

Institutions that want to avoid brokerage fees and commissions can conduct block trades directly on the fourth market. This term refers to a unique trading environment in the financial world. In the fourth market, institutional investors engage in direct securities trading through a private over-the-counter (OTC) computer network. Unlike conventional trading platforms like the New York Stock Exchange (NYSE) or Nasdaq, the fourth market bypasses recognized exchanges. The fourth market is exclusive and less transparent compared to the primary, secondary, and third markets accessible to all investors. It restricts trading to institutions, and transactions become public only after completion. This exclusive nature eliminates the risk of market price fluctuations before a transaction concludes, as other investors cannot intervene.

Insider Trading Potential

The fourth market also prevents block house traders from engaging in fraudulent practices like front running, a form of insider trading. In 2013, a senior equity trader at Cushing MLP Asset Management used advanced knowledge of block trades to profit personally, compromising his clients' interests.

Block House Example

In the context of block house trading, imagine a hedge fund aiming to sell a large amount of stock without disrupting the market. Instead of using public exchanges, the hedge fund partners with a block house broker, such as Cantor Fitzgerald. They approach potential buyers discreetly, revealing only a fraction of the shares initially. This method generates more interest and allows for controlled negotiations, resulting in a stable transaction between the hedge fund and interested buyers.


Block houses play a crucial role in facilitating large-scale block trades between institutional buyers and sellers. These trades, often involving substantial assets, are executed off-exchange to prevent market disruption. While the fourth market offers institutions a direct block trading avenue with reduced risks, block houses remain vital intermediaries in ensuring seamless and efficient transactions within the institutional trading landscape.

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Hexn operates under HEXN (CZ) s.r.o. and HEXN Markets LLC. HEXN (CZ) s.r.o. is incorporated in the Czech Republic with the company number 19300662, registered office at Cimburkova 916/8, Žižkov, Praha. HEXN (CZ) s.r.o. is registered as a virtual assets service provider (VASP). HEXN Markets LLC is incorporated in St. Vincent and Grenadines with the company number 2212 LLC 2022, registered office at Beachmont Business Centre, 379, Kingstown, Saint Vincent and the Grenadines